In general, a slide fastener is formed, for example, by attaching a coil-shaped or zigzag-shaped continuous fastener element to a fastener tape. In this case, the coil-shaped or zigzag-shaped continuous fastener element is manufactured by extruding a thermoplastic synthetic resin material to mold a linear monofilament, pressing a part of the obtained monofilament at a constant interval to mold a coupling head, and molding the monofilament in a coil shape or a zigzag shape.
Moreover, in a slide fastener having such a continuous fastener element, a method of applying a lubricating material to the outer circumferential surface of the fastener element in order to allow a slider to smoothly slide along the element row or to allow the left and right element rows to smoothly engage with each other is known.
For example, as illustrated in FIG. 13, JP 1-19888 B (Patent Document 1) discloses a configuration in which fine grooves or concave portions 62 are formed on an outer circumferential surface of a fastener element 61 in order to apply a lubricating material to the fastener element 61. Moreover, as an example of a method of forming fine grooves or concave portions 62 on the outer circumferential surface of the fastener element 61, Patent Document 1 discloses a method of forming fine uneven portions around a discharge opening of an extrusion nozzle that extrudes a monofilament to extrude the monofilament from the nozzle and rubbing an outer circumferential surface of the monofilament with a rough surface formed of fine particles or performing a process (for example, a sand blast process) of blasting fine particles with air.
By forming fine grooves or concave portions 62 on the outer circumferential surface of the continuous fastener element 61 in this manner, the lubricating material applied to the fastener element 61 is embedded in the grooves or concave portions 62, and the lubricating material can be properly attached to the fastener element 61. Thus, even when the slide fastener having the fastener element 61 is cleaned, for example, and external force is applied to the lubricating material applied to the fastener element 61 due to the cleaning, it is possible to prevent the lubricating material from being separated from the fastener element 61. Thus, even when the slide fastener is cleaned repeatedly, it is possible to maintain the effect of the lubricating material and to smoothly perform sliding of the slider and the engagement of the element rows over a long period of time.